The present invention relates to a slicing machine and a method of control for the machine. Such machines are principally, but not exclusively used for slicing food products, particularly slicing cheese, meat and pressed or moulded meat products.
Typically such a slicing machine includes a rotating blade and means to feed the product forward towards the blade so that successive slices are cut from one face of the product. The distance through which the product is advanced between successive cuts of the blade determines the thickness of the slices. Where the product is of uniform shape and density then it may be sufficient to use a single predetermined slice thickness to give a slice or group of slices of the required weight. In general however variations in the shape and density of the product mean that the weight of a slice of a given thickness varies. A previous approach to dealing with this variation is described and claimed in the applicants' granted European Patent EP-B-0,127,463. This patent describes and claims a process in which an automatic slicing machine is programmed to vary the thickness of the slices in accordance with a typical weight distribution for the product. Although this system achieves good results where the product shape or envelope varies in a predictable manner it still tends to produce a number of slices which are outside the required weight range when the actual weight density distribution departs from the expected distribution.
It has previously been proposed to make some determination of the cross-sectional area of the product as it is cut. This may be done using feelers disposed around the product in the vicinity of the slicing zone, or, for example, by placing a light source and a photodetector array in front of the cut face of the product. The area of the array which is illuminated by the image of the cut face is then used as an indication of the cross-sectional area. Although such a system is better able to cope with variations in the shape of the product it still tends to produce slices which are off-weight when there is variation in density of the product. This is a particular problem when the product is inhomogeneous. For example, bacon comprises both portions of fat and portions of lean and the different proportions of fat to lean vary from slice to slice producing unpredictable variations in the overall slice density.